Cooler Temperatures Spare Many Coral Reefs

November 6, 2009

Scientists said Thursday that lower-than-feared sea temperatures this summer gave a break to fragile coral reefs across the Caribbean and the central Gulf of Mexico that were damaged in recent years, the Associated Press reported.

Many of the creatures that make up coral have had to expel the colorful algae they live with, creating a bleached color due to the unusually warm water in recent years. However, the coral itself will die and damage the environment where many fish and other marine organisms live, should the problem continue.

C. Mark Eakin, coordinator of the National Oceanic and Atmospheric Administration’s Coral Reef Watch network, said they dodged a bullet this year, but the good news was that temperatures didn’t get quite warm enough for there to be a large-scale bleaching problem.

He and many other scientists gathered in Puerto Rico’s capital for a meeting of the U.S. Coral Reef Task Force.

In 2005, hot seas caused bleaching of as much as 90 percent of corals in the eastern Caribbean and killing more than half.

It was considered the worst coral bleaching in the region’s recorded history.

The Coral Reef Watch network warned in July that high temperatures this year might lead to severe coral problems because sea surface temperatures in parts of the Caribbean were unusually hot.

The threat had passed for 2009, since temperatures are now cooling, but the problem could return, Eakin said.

He added that researchers were seeing little signs of coral recovery in the Caribbean, where the damage has been “like a ratchet wrench clicking down and staying there”.

“Temperatures could be severe enough next year,” Eakin warned.

Known to be a fragile organism, reef-building coral is a tiny polyp-like animal that builds a calcium-carbonate shell around itself and survives in a symbiotic relationship with types of algae — each providing sustenance to the other.

But even a 1.7-degree Fahrenheit rise in normal maximum sea temperatures can disrupt that relationship.

When sea temperatures rise just a few degrees above average in the warmest summer months, bleaching can occur. And it can kill the organisms that rely on the algae for sustenance if it lasts more than a week.

Eakin and scientists in the British Caribbean dependency say some coral bleaching was recorded this year in the Cayman Islands.

But officials are still calculating the damage to local reefs, according to Croy McCoy, a senior researcher with the islands’ Department of Environment.